Manufacturers of optical transport systems now offer an ever-increasing amount of available capacity on individual optical fibers. For this reason, achieving fast self-healing in a network from an accidental failure is of paramount importance. Presently, SONET/SDH ring networks comprise the most common type of self-healing network design. While SONET/SDH ring networks offer quick restoration and are easy to implement, such ring networks are not cost effective for many applications. For example, a highly connected network with most of the nodes each having at least three links requires more spare capacity when designed in a ring configuration than a comparable design with mesh configuration in which spare capacity is shared by the entire network more efficiently.
While mesh networks achieve more efficient use of spare capacity, restoration in a mesh network is more complex and slower than in a ring network. One type of mesh network restoration scheme is Link-Based Restoration (LBR) in which failed traffic is restored between the two nodes adjacent to the failure location regardless of the originating and terminating nodes of the failed signals. Another mesh restoration scheme is Path-Based Restoration (PBR) in which failed traffic is restored between the pairs of nodes where the failed signals originate and terminate regardless of the failure location. PBR requires less spare capacity to effect restoration as compared to LBR. On the other hand, PBR algorithms for establishing alternate paths when a failure occurs are more complex and therefore PBR may be slower, as compared to LBR.
Utilizing pre-computed routes can increase the PBR speed. One proposed restoration path computation approach employs node and link disjoint restoration paths. link- and node-disjoint restoration path is a path (i.e., a collection of individual channels in a series of links, each coupling a pair of nodes) that does not share any link or any intermediate node with the original path. However, accomplishing PBR using node-and link-disjoint restoration paths is inefficient in terms of maintaining sufficient spare capacity. On the other hand, it is necessary to determine which of the links on the signal path failed in order to implement a PBR method using unrestricted restoration paths. It is often problematic to make such a determination at the endpoint nodes. Further, computing a restoration path that is distinct from other restoration paths when multiple paths fail simultaneously is often not fast.
Thus, there is a need for a restoration technique that is not restricted to link-and node-disjoint paths, thus making the most efficient use of spare capacity. Additionally, there is a need for a mesh network restoration technique that affords restoration speeds comparable to those achieved in SONET/SDH rings. Further, there is a need for a mesh network restoration technique that is self-healing and self-managing.